1. Technical Field
The present invention relates to a horizontal LED device and a method of manufacturing the same. More particularly, the present invention relates to a high-power and high-efficiency horizontal LED device, which is manufactured by using the advantages of conventional horizontal and vertical LEDs, and a method of manufacturing the same.
2. Background Art
Generally, as shown in FIG. 1a, a horizontal LED device is configured in the basic form of a light-emitting structure including one light-emitting active layer (MQWS) and two cladding layers (p-GaN, n-GaN) covering both sides of the active layer. The cladding layers making contact with electrodes are n-doped and p-doped, respectively. The cladding layer making contact with a substrate is n-doped, and the other cladding layer is p-doped. When voltage is applied to each of the doped cladding layers through an electrode in accordance with the polarity thereof, the n-doped cladding layer supplies electrons, and the p-doped cladding layer supplies holes. At this time, electric current flows, and simultaneously these electrons and holes are combined in the active layer disposed between the cladding layers, thus emitting light. The substrate reflects or transmits the light emitted from the active layer according to the wavelength thereof. As the substrate, a sapphire substrate having low thermal conductivity and insulation properties is generally used. Such a horizontal LED device has a low current spreading effect and a high current crowding effect, emits light non-uniformly, and has a small emitting area per chip. Therefore, this horizontal LED device is disadvantageous for use in a large area.
As shown in FIG. 1b, a flip-chip LED device is configured such that the horizontal LED device is overturned and then fixed on a silicon sub-mount by a stud bump. Therefore, this flip-chip LED device is actually identical to the horizontal LED device in terms of a basic structure for light emission. Since the flip-chip LED device emits light through a substrate, light extraction is improved, thus exhibiting excellent heat radiation characteristics and high power characteristics. However, this flip-chip LED device additionally requires a sub-mount and a soldering process.
As shown in FIG. 1c, a vertical LED device (thin GaN) maintains an original form in which a part of a laminate is not removed by etching in terms of a basic structure for light emission. Generally, the basic structure of the vertical LED device is accomplished by the steps of: sequentially a bonding reflector and a receptor onto a cladding layer; forming an electrode; separating a substrate; and forming an electrode on a cladding layer of the separated substrate. The vertical LED device is configured such that the light emitted from the active layer thereof is vertically reflected from a reflective plate and then discharged upwardly. Thus, this vertical LED device has excellent heat radiation characteristics and high power characteristics. Such a vertical LED device has a high current spreading effect and a low current crowding effect, emits light uniformly, and has a large emitting area, and so this vertical LED device is advantageous for use in a large area. However, this vertical LED device has a problem of complicated processes and a low yield.
Therefore, it is required to develop a novel LED device for overcoming the disadvantages of a conventional LED device and a manufacturing method thereof.